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CHAPTER XVIII
ELECTROLYSIS

The subject of the electrolysis of underground pipe systems is
closely allied to that of bonding. Beginning with the rather
general introduction of the direct current street railway systems
in the early nineties, with their track return and relatively poor
bonding, and extending through the rapid development and
improvement of such systems, the question of electrolysis, its
cause and prevention has maintained an important place in the
discussions of the engineers of gas and water works corporations
as well as the telephone and street railway interests.

It has, of course, been known for a long time that if a direct
current be allowed to flow from a metal electrode, through an
electrolyte to a second metal electrode, a chemical reaction takes
place at the expense of the positive plate, i.e., this plate is actually
eaten away, the metal removed therefrom forming a salt with
some of the acid radicals of the electrolyte. During these reac-
tions which take place similarly when moist earth is the electro-
lyte it was noticed that hydrogen was given off at the cathode or
negative terminal while oxygen was liberated at the anode. It
was supposed for some time that those free gases were formed
from the decomposition of the water in the earth. When it was
later found, however, that this action often took place with poten-
tials between terminals of the order of hundredth® and even
thousandths of a volt, which are not sufficient to decompose water
and free these gases at their respective electrodes, a further
study of the problem was undertaken.

Experiments carried on at the University of Wisconsin and
recorded in the discussion of a very able paper upon this subject
presented before the American Institute of Electrical Engineers
by the late Isaiah H. Farnham in 1894 demonstrated the fact that
with iron electrodes embedded in moist earth electrochemical
action is substantially as follows: Most earths contain salts of
alkaline metals. Merely a directive electromotive force of the
order of 0.001 volt will cause the acid radical of these salts to be

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